Purifying nitriles



Reissued Feb. 15, 1949 UNITED STATES .esrenr OFFICE Anderson W. Ralston, Chicago,

Lowell '1. Crews,

Homewood, and Edwin WV. Colt, Evanston, 111., and Company, Chicago,

assignors to Armour lit, a corporation of I llinois No Drawing. Original No. 2,401,772, dated June 11, 1946, Serial No. 537 piication for reissue N 7 Claims.

This invention relates to processes of purifying nitriles and it comprises processes wherein crude unconjugated higher fatty acid nitriles are heated in the presence of maleic anhydride for the removal of impurities.

The manufacture of higher fatty acid nitriles from the corresponding fatty acids is now an industry of considerable magnitude. Such nitriles are made by processes broadly consisting in reacting the fatty acid with ammonia. The resulting; nitriles may be distilled, or otherwise worked up to free them of any unreacted fatty acid, side-reaction products, etc. Crude fatty acid nitriles, however, are quite odoriferous, and have rather pronounced color, usually of a reddish hue. For many uses it is desirable to have nitriles which are of lighter color, and which are of more satisfactory odor. The present invention is based on discoveries of ways by which certain crude nitriles can be improved with respect to color and odor.

We have now discovered that maleic anhydride has the property of reacting with, or otherwise associating itself with the color and odor-yielding bodies in unconjugated crude nitriles, and that by heating the nitrile in the presence of small amounts of maleic anhydride these impurities in the nitrile can be removed.

Our invention is applicable to the purification of all unconjugated fatty acid nitriles. For the purposes of this invention, the term unconjugated fatty acid nitriles will be used to designate those fatty acid nitriles which contain no conjugate double bonds. This invention does not relate to conjugated fatty acid nitriles such as 9,11-octadecadienenitrile, eleostearonitrile, and the like. Since these materials themselves react with the maleic anhydride to form lA-addition products the maleic anhydride could not also react completely with the impurities and therefore no effective purification could be obtained.

Commercially, the unconjugated fatty acid nitriles to which our invention relates have from six to eighteen or more carbon atoms, the eighteen carbon atom nitriles such as those from or oleic acid being especially. valuable materials commercially. The nitriles of fish oil fatty acids, having as many as 26 carbon atoms, are also important materials. Our invention includes the treatment of any of the unconjugated fatty acid nitriles. saturated and unsaturated, and having at least 6 carbon atoms.

We shall now describe a specific practice of our invention with reference to the purification of .oleic acid nitrile, since this is representative of ,370, May 25, 1944. Apovembcr 10, 1948, Serial the unconjugated fatty acid nitriles as a whole.

To 100 parts of the oleic acid nitrile we add about 1 to 2 parts of maleic anhydride and then heat this mixture to a temperature of about 175 C. for a short period of time, 10 minutes being generally sufficient. Under these conditions the maleic anhydride combines with the color and odoriferous constituents in the nitrile. Thereafter the nitrile is allowed to cool down, is washed with water to remove water-soluble reaction products of the maleic anhydride and the impurities in the nitrile, and, if desired, the nitrile is thereafter distilled.

The elevated temperature above referred to is not critical, but the higher temperatures do speed up the combination of the maleic anhydride with the impurities.

advantageously, the temperature is from about 100 C. to 200 0., but below the boiling point of the nitrile, in the nitrile.

Nor is the amount of added maleic anhydride critical. One or two percent is usually enough since the amount of impurities in the nitrile is relatively small. More maleic anhydride can be added if one or two percent appears insufficient to improve the color and odor.

All the other unconjugated 'iatty acid nitriles can be purified in substantially the same manner.

Having thus described our invention, what we claim is:

l. The process of purifying an unconjugated iatty acid nitrile which comprises heating the nitrile with a amount of maleic anhydride and washing the thus treated nitrile with water.

The process of purifying an unconjugated atty acid ni' le which comprises heating the erature of about 190 C. to 200 but below the boiling point of the nitrile, in presence of a small amount of maleic ande, washing the thus treated nitrile with water.

3. The process of purifying an unconjugated *tty acid nitrile which comprises heating the .c with a small amount of maleic anhydride, washing the thus treated nitrile with water, and. distilling the nitrile.

4. The process or" purifying an unconjugated fatty acid nitrile which comprises heating the e to a temperature of about 169 C. to 200 C., below the boiling point of the nitrile, in the pr se ce of a small amount of maleic anhydride, w. g the thus treated nitrile with water, and distilling the nitrile.

In a process for purifying an unconjugated 3 :iietty acidnitrile the step of heating the nitrile in the presence of maieic anhydride.

6. In a process for purifying an unconjugated fatty acid nitrile the step of heating the nitrile to a temperature of about 100 C. to 200 (3., but below the boiling point of the nitriie, in the presence of maleic anhydride.

T. A process of purifying an unconjugated fatty acid nitriie which comprises heating the nitrile in the presence of maleic anhydride to form reaction products of said maleic anhydride with impurities contained in the nitrile, and. removing said reaction product from the nitrile.

ANDERSON W. RALSTON. LOWELL T. CREWS. EDWIN W. COLT.

No references cited. 

